• InSite Intelligence


By Hari Kumaragurubaran

As the COVID-19 virus spreads in the US and around the world, accessible and actionable information is crucial for public health providers. With hospitals facing an unprecedented surge in patients an effective heating, ventilation and air conditioning (HVAC) system becomes indispensable from an operational standpoint.

Every hour of the day, the HVAC system contributes to the overall goal of not only maintaining patient comfort but also suppressing Hospital-acquired infections. Hospital-acquired infections (HAIs), also known as nosocomial infections, are infections that patients get while receiving treatment for medical or surgical conditions. Environmental contaminants—viruses, bacteria, mold/fungi—and biogenic contaminants—pollen, mites, protozoans, airborne cystic spores—play a role in the spread of these infections and are influenced by HVAC systems.

According to research by the Centers for Disease Control, one in 25 patients in the US will suffer at least one infection acquired in the healthcare environment. In 2011, that worked out to about 722,000 incidents. In the current scenario, it becomes critical to reduce the proliferation of Hospital-acquired infections.

This is where the benefit of technology comes into play via Fault Detection and Diagnostics (FDD). The FDD tool collects data points in the HVAC control system in real-time (temperatures, flows, pressures, actuator control signals, damper positions, etc.), and these data points are run through a set of algorithms/rules, which help to detect anomalies in the parameters being monitored. Due to the simplicity and transparency of these rules, coupled with technology gains made in collecting vast amounts of data, FDD helps to detect possible risks leading to the spread of Hospital Acquired Infections.

A summary of how Fault Detection Diagnostics Tools can help in avoiding the proliferation of Hospital Acquired Infections-

- Ventilation- Dilution ventilation helps to control infectious particles by introducing outdoor air, usually 2 to 5 air changes/hour (ACH), to dilute space air and to exhaust contaminated air. FDD will help detect deviations in acceptable Indoor Air Quality and Ventilation requirements

- Pressurization- Pressurization protects against cross-contamination from the infiltration of air from one space type to that of another. This is of great importance in healthcare settings, but it can be challenging to control. FDD tools will continuously monitor the static pressure associated with critical zones and will help identify anomalies when pressurization requirements aren’t met.

- Temperature & Moisture- Controlling Temperature & moisture can help prevent the spread of pathogens, which tend to multiply in a humid environment. FDD tools will constantly monitor Temperature and RH values to detect deviation.

Example: Identifying Ventilation Issues

Summary: The BAS was closing the outside air (OA) damper on AHU-4 to the minimum position despite high levels of CO2 in the space being served by the unit.

Details: The air handlers in common-use spaces are equipped with demand control ventilation, which modulates the intake of outside air based on CO2 levels measured in the space. However, during certain portions of the day, the BAS would bring the OA damper on AHU-4 to minimum position even though CO2 levels in the space were continuing to rise — resulting in rapidly increasing CO2 levels in the space when the OA damper was at minimum position. AHU-4 CO2 levels tracked closely with AHU-5’s, yet AHU-5’s OA damper would stay at maximum position, which would keep the CO2 in the space at an acceptable level. The BAS contractor was brought in to review and revise the demand control sequence for AHU-4, which improved the issue.

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